Dataset Information

Protocol for topology-preserving smoothing of BOLD fMRI retinotopic maps of the human visual cortex.

ABSTRACT: The hierarchical organization of the visual system preserves topology, which is often lost in the "raw" human retinotopic maps derived from BOLD fMRI recordings. Here, we present the protocol for generating topology-preserving and smooth retinotopic maps from human retinotopy fMRI data. We describe data pre-processing, 3D surface flattening, and selection of the region of interest (ROI), followed by smoothing of the retinotopic maps within the ROI. This approach can be applied to visual cortical areas V1, V2, and V3 simultaneously. For complete details on the use and execution of this protocol, please refer to Tu et al. (2021).

SUBMITTER: Tu Y

PROVIDER: S-EPMC9389414 | biostudies-literature | 2022 Sep

REPOSITORIES: biostudies-literature

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Protocol for topology-preserving smoothing of BOLD fMRI retinotopic maps of the human visual cortex.

Tu Yanshuai Y Li Xin X Lu Zhong-Lin ZL Wang Yalin Y

STAR protocols 20220811 3

The hierarchical organization of the visual system preserves topology, which is often lost in the "raw" human retinotopic maps derived from BOLD fMRI recordings. Here, we present the protocol for generating topology-preserving and smooth retinotopic maps from human retinotopy fMRI data. We describe data pre-processing, 3D surface flattening, and selection of the region of interest (ROI), followed by smoothing of the retinotopic maps within the ROI. This approach can be applied to visual cortical ...[more]

PMID: 35990746

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Project description:The localization of visual areas in the human cortex is typically based on mapping the retinotopic organization with functional magnetic resonance imaging (fMRI). The most common approach is to encode the response phase for a slowly moving visual stimulus and to present the result on an individual's reconstructed cortical surface. The main aims of this study were to develop complementary general linear model (GLM)-based retinotopic mapping methods and to characterize the inter-individual variability of the visual area positions on the cortical surface. We studied 15 subjects with two methods: a 24-region multifocal checkerboard stimulus and a blocked presentation of object stimuli at different visual field locations. The retinotopic maps were based on weighted averaging of the GLM parameter estimates for the stimulus regions. In addition to localizing visual areas, both methods could be used to localize multiple retinotopic regions-of-interest. The two methods yielded consistent retinotopic maps in the visual areas V1, V2, V3, hV4, and V3AB. In the higher-level areas IPS0, VO1, LO1, LO2, TO1, and TO2, retinotopy could only be mapped with the blocked stimulus presentation. The gradual widening of spatial tuning and an increase in the responses to stimuli in the ipsilateral visual field along the hierarchy of visual areas likely reflected the increase in the average receptive field size. Finally, after registration to Freesurfer's surface-based atlas of the human cerebral cortex, we calculated the mean and variability of the visual area positions in the spherical surface-based coordinate system and generated probability maps of the visual areas on the average cortical surface. The inter-individual variability in the area locations decreased when the midpoints were calculated along the spherical cortical surface compared with volumetric coordinates. These results can facilitate both analysis of individual functional anatomy and comparisons of visual cortex topology across studies.

Dataset Information

Protocol for topology-preserving smoothing of BOLD fMRI retinotopic maps of the human visual cortex.

Publications

Protocol for topology-preserving smoothing of BOLD fMRI retinotopic maps of the human visual cortex.

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